NEW CORRECTED QT FORMULA OPTIMAL FOR DIFFERENT HEART RATES: A COMPARATIVE STUDY

Abstract

Introduction: In an Electrocardiogram (ECG), QT Interval (QTI) has gained a major role as an indicator; its prolongation leads to ventricular arrhythmias. QTI varies with RR Interval (RRI) as the Heart Rate (HR) changes which motivate to measure corrected QT (QTc) interval for different HR. Objective: To develop a new QTc formula optimal for different HRs and compare its performance with previously developed QTc formulas. Methods: ECGs were recorded from 220 volunteers (110 females) in Sinus Rhythm (SR), Sinus Tachycardia (ST) and Sinus Bradycardia (SB) conditions. HR, RRI and QTI were extracted from the lead II. A New QTc formula was developed by taking the mean value of slopes between RRI and QTI in SR, ST, and SB. The QTc values were calculated using a newly developed formula, and the performance was compared with previously developed QTc formulas. Results: In SR, ST, and SB, the QTI mean values for lead II were 358 ms, 316 ms, and 440 ms and the mean slope values between RRI and QTI were 0.132, 0.214, and 0.137, respectively. The new QTc (QTcN) formula was developed by taking the mean of the above slope values as 0.161 and mentioned as QTcN[Formula: see text]QT[Formula: see text]0.161(1000−RRI). Conclusion: The least slope value of the QTI/RRI plot gave the best correction formula. Using statistical analysis, it was noted that Frederica QTc formula showed the best results for SR and SB and Hodge’s formula in ST. To overcome the limitation of QTc formulas for different HR, a QTcN formula was developed to reduce over/under estimation of QTI.